This invention relates to a printing head for an ink-jet printing apparatus in which hollows for ink-flow passages (channels) are formed in the spaces between each of a plurality of plates are laminated.
A prior art ink-jet printing head, as shown in FIG. 1, comprises a first plate 1 having two hdllows 1a, 1b which are of different depths and which serve as the ink flow passages. An ink flow passage is formed to serve as a pressure chamber 3 by a second plate 2 arranged on plate 1 over the hollow 1a. Another ink flow passage is formed to make an outlet passage 4 by the second plate 2 overlying the hollow 1b. Ink is filled inside of these passages. The second plate 2 is normally drilled or etched to form a nozzle 2a as the outlet passage 4, together with the ink flow passage formed by the hollow 1b. A piezoelectric transducer 5 is provided on plate 2. The piezoelectric transducer 5 inwardly deflects a flexible wall, i.e., a flexible portion of the second plate 2 that serves as a wall of pressure chamber 3, to reduce the volume of the pressure chamber 3 so that ink can be jetted out from the pressure chamber through the ink outlet passage 4.
The ink outlet passage 4 is so designed as to be very small in the cross-sectional area of its passage compared with that of the pressure chamber 3, because of the necessity of ink-jetting. The ink outlet passage 4 is required to have a definite length (in the thickness direction of plate 2) to optimize the jetting performance of ink droplets. In summary, in the conventional ink-jet printing heads, a first plate 1 has been etched to form a two-step hollow. Hollow 1b has been provided in addition to the hollow 1a to form an ink flow passage, hollow 1b serving as a portion of the ink outlet passage. The hollow 1b must not only be shallower in depth but also narrower in width than the hollow 1a.
The above-described conventional ink-jet printing head is disadvantageous in that a large amount of manufacturing time is required, and also because of the high cost to etch the first plates 1 in a two-stepwise manner as described above.
It is an object of the invention to provide a printing head for an ink-jet printing apparatus which can be readily manufactured at a substantially reduced cost.